refactor(@ngtools/webpack): adjust types to support strict mode

Author: clydin

packages/ngtools/webpack/src/utils.ts

@@ -18,7 +18,7 @@ export function workaroundResolve(path: Path | string): string {
 }
 
 export function flattenArray<T>(value: Array<T | T[]>): T[] {
-  return [].concat.apply([], value);
+  return ([] as T[]).concat.apply([], value);
 }
 
 // TS represents paths internally with '/' and expects paths to be in this format.

packages/ngtools/webpack/src/virtual_file_system_decorator.ts

@@ -60,7 +60,7 @@ export class VirtualFileSystemDecorator implements InputFileSystem {
     (this._inputFileSystem as any).readJson(path, callback);
   }
 
-  readlink(path: string, callback: (err: Error, linkString: string) => void): void {
+  readlink(path: string, callback: (err: Error | null | undefined, linkString: string) => void): void {
     this._inputFileSystem.readlink(path, callback);
   }